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      <title>MySQL表约束详解 - 交互式测验</title>
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          <div class="quiz-container">
            <div class="quiz-header">
              <h1>MySQL表约束详解 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
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      <script>
        const quizData = [
  {
    "question": "根据文档，与唯一约束（Unique Key）相比，主键约束（Primary Key）一个最核心的特性是什么？",
    "options": [
      "允许包含多个NULL值",
      "必须是非空的（NOT NULL）",
      "不能自动创建索引",
      "主要用于业务逻辑而非实体唯一标识"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档明确指出了主键约束的三个特性：唯一性、非空、自动创建索引。其中，“非空”是它与唯一约束的一个关键区别，因为唯一约束通常允许有一个（或多个，取决于具体数据库实现）NULL值，而主键约束绝对不允许为NULL。",
    "source": "文档中「2.1 主键约束（Primary Key）」部分",
    "hint": "回顾文档中列出的主键的三个特性，其中有一个是唯一约束所不强制要求的。"
  },
  {
    "question": "在外键约束的级联操作中，如果定义了 `ON DELETE CASCADE`，当主表中的某条记录被删除时，将会发生什么？",
    "options": [
      "数据库会阻止主表记录的删除操作，并报错",
      "子表中对应的外键字段将被自动设置为NULL",
      "子表中所有引用了该记录的关联记录将被同步删除",
      "只有在子表没有关联记录时，主表记录才允许被删除"
    ],
    "correctAnswerIndex": 2,
    "explanation": "根据文档描述，`CASCADE` 级联操作意味着当主表数据发生删除或更新时，子表中相关的记录也会进行同样的操作。因此，`ON DELETE CASCADE` 会导致主表记录删除时，子表中的关联记录也一并被删除，以维持数据的引用完整性。",
    "source": "文档中「3.1 外键约束（Foreign Key）」部分",
    "hint": "思考一下 \"cascade\"（级联）这个词的含义，它暗示了一种连锁反应。"
  },
  {
    "question": "在电商系统的 `products` 表设计中，使用 `CHECK (price > 0)` 约束的主要目的是什么？",
    "options": [
      "为价格字段设置一个默认值",
      "确保商品价格在所有商品中是唯一的",
      "在价格被更新时触发一个级联操作",
      "保证数据的有效性，防止将商品价格录入为零或负数"
    ],
    "correctAnswerIndex": 3,
    "explanation": "`CHECK` 约束用于确保列中的值必须满足指定的布尔表达式。在这里，`price > 0` 的条件确保了任何插入或更新到 `products` 表的数据，其 `price` 字段的值都必须是正数，从而从数据库层面防止了无效数据的产生。",
    "source": "文档中「3.2 检查约束（Check）」和「4.2 商品表设计」部分",
    "hint": "CHECK 约束的核心功能是“检查”数据是否满足某个预设的业务规则。"
  },
  {
    "question": "根据“约束设计最佳实践”中的性能考量，我们应该如何权衡外键的使用？",
    "options": [
      "尽可能多地使用外键，因为它们能最大化保证数据完整性",
      "外键对性能没有影响，可以根据业务需求随意使用",
      "应避免过多外键，因为它们会在写入操作时增加验证开销，可能影响性能",
      "只在读多写少的表中使用外键，写密集的表应完全避免"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档在“性能考量”部分明确提出“避免过多外键影响写性能”。这是因为每次对子表进行插入或更新时，数据库都需要去主表检查外键引用的记录是否存在，这个额外的步骤会增加写入操作的耗时。因此，需要在数据完整性和写性能之间做出合理的权衡。",
    "source": "文档中「七、约束设计最佳实践」的「性能考量」部分",
    "hint": "思考一下，每次插入一条带外键的记录时，数据库需要额外做什么工作来验证它？"
  },
  {
    "question": "MySQL 8.0 引入的“不可见索引”（Invisible Index）主要解决了什么问题？",
    "options": [
      "创建一个只有特定用户才能看到的加密索引",
      "在不实际删除索引的前提下，安全地测试移除该索引对查询性能的影响",
      "为JSON或文本字段内容创建一种特殊的、不可见的索引",
      "自动隐藏不再被查询优化器使用的冗余索引"
    ],
    "correctAnswerIndex": 1,
    "explanation": "不可见索引对查询优化器是不可见的，但它在后台仍然会被正常维护。这使得DBA或开发者可以在不承担删除和重建索引的高昂成本下，将索引设置为“不可见”来模拟其被删除后的情况，从而安全、便捷地评估该索引的实际价值。",
    "source": "文档中「6.2 不可见索引」部分",
    "hint": "设想一个场景：你想知道删掉一个索引会不会让系统变慢，但又不敢真的删除它。这时你会希望索引有什么样的特性？"
  },
  {
    "question": "根据文档中推荐的命名规范，一个用于关联 `orders` 表（子表）和 `users` 表（父表）的外键，最合适的名称是什么？",
    "options": [
      "fk_orders_users",
      "fk_user_id",
      "foreign_key_orders",
      "users_orders_fk"
    ],
    "correctAnswerIndex": 0,
    "explanation": "文档在“约束设计最佳实践”的“命名规范”部分明确给出了外键的推荐命名格式为 `fk_子表_父表`。这种命名方式清晰地表明了这是一个外键约束，以及它所关联的两个表，极大地提高了数据库结构的可读性和可维护性。",
    "source": "文档中「七、约束设计最佳实践」的「命名规范」部分",
    "hint": "一个好的命名规范应该能清晰地表达出约束的类型、作用范围和关联对象。"
  },
  {
    "question": "在什么情况下，使用触发器（Trigger）来补充约束比使用标准的CHECK约束更为合适？",
    "options": [
      "当需要为字段设置一个静态默认值时",
      "当需要实现比标准约束更复杂的业务逻辑验证时，例如需要查询其他表的数据进行判断",
      "当需要确保一个字段值的唯一性时",
      "当需要实现简单的非空检查时"
    ],
    "correctAnswerIndex": 1,
    "explanation": "标准的CHECK约束通常只能对本行的数据进行简单的逻辑判断。而触发器则强大得多，它可以在数据插入、更新或删除前后执行一段代码逻辑，这段逻辑可以包含查询其他表、进行复杂计算等操作。因此，当约束条件依赖于其他表的数据或需要复杂逻辑时，使用触发器是更合适的选择。",
    "source": "文档中「5.3 触发器补充约束」部分",
    "hint": "考虑一下标准约束（如CHECK, NOT NULL）的能力边界，当验证逻辑超出这个边界时，就需要更强大的工具了。"
  }
];
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            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
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            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

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                '<div class="score-card">' +
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                '<div class="score-card">' +
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                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  